| 摘要 |
PURPOSE:To improve controllability for doping and uniformity of a surface, by forming second semiconductor layers of small electron affinity on a first semiconductor layer of large electron affinity and making the electron affinity smaller accordingly as the second semiconductor layers are increasingly away from an interface of the first semiconductor layer and besides providing the second layers with quantum wells in which donor impurities are added. CONSTITUTION:An undoped GaAs layer 52 is made to grow to serve as a channel part on a semi-insulating GaAs substrate 51, and undoped AlXGa1-XAs layers 54 are made to grow further thereon. Mol ratios (x) of the AlXGa1-XAs layers 54 are changed continuously to be x=0.3 to x=0.7 ranging from an interface formed between the GaAs layer 52 and the layers 54 to a gate electrode 56 which is formed later. Further, GaAs well layers 55, in which donor impurities are added, are formed in the AlXGa1-XAs layers. A three-layered electrode of Ti/Pt/Au is used as a gate electrode 56, and AuGe/Ni/Au is used so as to form a source electrode 57 and a drain electrode 58 by a lift-off method. |
